Recs.
Updated
DOS-derivated Operating System, fully compatible with various older DOS OSes (including MS-DOS, DR-DOS. PC-DOS, CP/M-86), with enhanced features added.
SpecsUpdate
Pros
Pro Highly portable OS
It takes ten minutes to make a portable, USB FreeDOS drive, All you need is a USB device FAT or FAT32 formatted (128 Mb should be enough, but a 2 GB device would be better). First make a FreeDOS bootable USB drive with a program like Rufus (on Windows) or UnetBootin (on linux or Mac). Select it at boot and run fdisk to make a Primary DOS partition and install FreeDOS on it. Final step: reboot and run fdisk again to make the new partition active (optional: delete the installer partition). After that, the system is ready to boot with any computer.
Cons
Con Unlikely going to be your PC main OS
If looking for a lightweight OS, and thinking of FreeDOS as a possible option, consider that it will only useful when having to deal with legacy software, or other dos-based programs still commonly used at workplaces. Nonetheless it's a fantastic solution for Retro-Gamers who still own a a supported sound card. However the lack of modern software makes it hard to accomplish common everyday tasks, such us opening a document written in UTF-8, not mentioning, obviously docx and pdf files. The best choice is to install it on a USB drive, in order to have a portable OS, with basic hardware and all your files (and if you want games) ready to be launched with every machine. Useful to edit partitions, as well as restore MBR, check errors, install a light bootmanager on any kind of FAT partiton of every IDE-mode compatible hard-disk.